Download 2.2.5-H.2.2.10 Respiration - Intermediate School Biology

2.2. Respiration summary
2.2.5 - H.L 2.2.10 Respiration
At the end of ths section you should be able to ….
1. Define the term: aerobic respiration.
2. Explain the role of aerobic respiration
3. Express aerobic respiration by a balanced equation.
4. Know respiration is a 2 stage process
5. Know stage 1 does not require oxygen and releases a small amount of energy, occurs in
cytosol
6. Know Stage 2 does require oxygen and releases a large amount of energy, occurs in
mitochondrion
7. Define anaerobic respiration. Know it is a first stage process
8. State the products of anaerobic respiration
9. State the cellular location of the first & second stage.
Contemporary issue
10. Explain the role of microorganisms in fermentation including bioprocessing with
immobilised cells: procedure, advantages and use in bioreactors
H.L.2.2.10
11. Know the first stage reaction: Glycolysis
12. Know the fermentation option: alcohol and carbon dioxide or lactic acid production
13. Know the second stage process: details of Krebs cycle and electron transport system
Mandatory activity: Prepare & show the production of alcohol by yeast
Key words
Aerobic respiration, anaerobic respiration, cytosol, fermentation, bioreactor, sodium
alginate, calcium chloride, glycolysis, iodoform, potassium iodide, sodium hypochlorite
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2.2. Respiration summary

Definition of aerobic respiration: Controlled release of energy from food using oxygen.

Role of aerobic respiration:
 Provide energy for cellular activity e.g. protein synthesis, DNA replication, and cell
division.
 Provides carbon dioxide for photosynthesis.
 Balanced equation:
C6H12O6 + 6O2 = 6CO2 + 6H2O + energy.
Stages of respiration
Respiration is a two stage process:
 The first stage does not require oxygen and releases a small amount of energy;
 The second stage does require oxygen and releases a large amount of energy.
Note: Further detail on stages 1 and 2 under higher level P 3
 First stage process
Anaerobic respiration may occur in the presence of oxygen but does not use oxygen. It is therefore
a first-stage process.
Anaerobic respiration is also known as Fermentation.
The products of Fermentation (anaerobic respiration) are lactic acid or alcohol and carbon dioxide.
Fermentation (Anaerobic respiration):
Glucose
alcohol + carbon dioxide.
or
Glucose

Lactic acid.
Second-stage process
Aerobic respiration uses oxygen and is described as a second-stage process.
C6H12O6 + 6O2 = 6CO2 + 6H2O + energy.
Cellular location of the first and second stage process:
 The first stage process occurs in the cytosol (the cytoplasm minus the organelles).
 The second stage process occurs in the mitochondrion.
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2.2. Respiration summary
Contemporary issue:
Role of micro-organisms in industrial fermentation
Industrial fermentation:




The use of micro-organisms to make a product e.g. alcohol or bread
Also known as bioprocessing
Carried out on a large scale in vessels called bioreactors.
Can be carried out using immobilized enzymes (cells). Enzymes are attached to an inert
material e.g. sodium alginate
Procedure
1.
2.
3.
4.
5.
Yeast is mixed with a sodium alginate .
Drops of the mixture are added to a calcium chloride solution.
Small beads with live, trapped yeast are formed.
Nutrients can diffuse through the beads to the live yeast.
The product will diffuse from the yeast .
Advantages of Immobilised
Enzymes
Sodium alginate with
entrapped enzyme
Uses of immobilised enzymes (cells)



To make alcohol
To produce glucose
To make lactose-free milk
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1. Easy recovery of
enzymes for reuse.
2. Easy recovery of
products (no enzyme
contamination).
3. Greater enzyme
stability.
2.2. Respiration summary
H. 2.2.10 Higher level
STAGE 1: GLYCOLYSIS


The first stage process is referred to as Glycolysis
Converts a six-carbon carbohydrate (glucose) to pyruvate with the
generation of a small amount of ATP.
Under anaerobic conditions:
 the pyruvate molecule is converted or reduced to alcohol and
carbon dioxide in most plant cells and yeast.
or
 the pyruvate molecule is reduced to lactic acid in most animal
cells and
many bacteria
STAGE 2: KREBS CYCLE/ELECTRON TRANSPORT SYSTEM
In the second stage process under aerobic conditions, a series of
reactions occurs:

the pyruvate molecule enters the mitochondrion and is broken down to one molecule of
carbon dioxide and a two-carbon acetyl group, acetyl Co-enzyme A.

This Acetyl Co A enters a series called Krebs Cycle and leaves it later as CO2 and H2O.

During this cycle an electron transport system operates to remove electrons from the
substrate intermediates

Electrons from the cycle are transferred through an electron transport chain (inner
membrane of mitochondrion)

Ultimately these are transferred to oxygen which combines with hydrogen to form water

The energy released by these electrons through the chain is used in the production of ATP
molecules (a large amount of energy is produced).
Note: The electron transport system cannot work in the absence of oxygen.
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2.2. Respiration summary
i) PREPARE AND (ii) SHOW THE PRODUCTION OF ALCOHOL BY YEAST
MATERIALS/EQUIPMENT
Yeast
Glucose
Sodium hypochlorite solution
Potassium iodide solution
Fermentation locks
DIAGRAM
(i) To prepare alcohol using yeast
PROCEDURE
(i) To prepare alcohol using yeast
1. Add yeast and glucose to conical flask A.
2. Add glucose to flask B. This acts as a control .
3. Attach a fermentation lock to each flask.
4. Place both flasks in the incubator at 30 oC overnight.
(ii) To show the presence of alcohol: Iodoform test for alcohol
1. Filter the contents of each flask into test tubes.
2. To each test tube, add potassium iodide solution
and sodium hypochlorite solution.
3. Transfer to a water bath for 4-5 minutes.
4. Allow to cool.
5. Record and compare results.
6. Replicate the investigation.
A
Yeast and glucose
Results
Flask
Yeast and glucose
solution
Control (no yeast)
Original colour of
filtrate
Clear
Final colour filtrate
Clear
Clear
Yellow crystals
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B
Glucose (control)